Gets everything free but in vain (3,3,7)

I believe the answer is:

all for nothing

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'vain' is the definition.
Both the answer and definition are adjectives.
Perhaps you can see an association between them that I don't see?

'gets everything free but' is the wordplay.
I cannot quite understand how this works, but
'everything' could be 'all' (all things) and 'all' is found in the answer.
'free' could be 'fornothing' (I've seen this in another clue) and 'fornothing' is found in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).

'in' acts as a link.

Can you help me to learn more?

I've seen this clue in The Globe and Mail.

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